The Gnumeric Manual
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# 14.7. Fourier Analysis Tool

Figure 14-26. Fourier Analysis Tool Dialog

The Fourier Analysis tool normally performs a Fast Fourier Transform to obtain the discrete fourier transform Fs of the given sequence ft of real numbers according to the formula given in Figure 14-27.

Select the "Inverse" option to calculate the inverse discrete fourier transform ft of the given sequence Fs of real numbers

| If the given sequences does not contain a number of terms that is a power of 2 (i.e. 2, 4, 8, 16, 32, 64, 128, etc.), this tool will append zeros to reach such a power of 2!

Specify the cells containing the datasets in the "Input Range" entry. The entered range or ranges are grouped into sequences either by rows or by columns.

If you have labels in the first cell of each data set, select the "Labels" option.

Figure 14-27. Fourier Analysis Formulae

Before using the numbers obtained by this tool, ensure that these are in fact the correct formulae for your discipline. In the physical sciences this fourier transform tends to be called the inverse fourier transform and vice versa. Moreover, frequently the scaling factor varies.

For example Mathematica uses the terms fourier transform and inverse fourier transform with the reversed meaning than Gnumeric and it uses a scaling factor of 1/SQRT(N) rather than 1/N.

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